JPH07167474A - Control method for heater circuit of air conditioner - Google Patents

Abstract

PURPOSE:To provide a control method for a heater circuit which detects a wire breakage and short-circuiting of a heater circuit to perform a phase control by using a switching element, and also performs a failure diagnosis including a phase circuit control signal part. CONSTITUTION:A phase operation is performed by a triac 2 for a set period of time after the start of a power connection to an auxiliary heater 4. A current value at that time and a previously set current value are compared by a current transformer 3 which detects a current flowing on the auxiliary heater 4. When the detected current value is large, and the current value does not change even when a phase control is performed, a judgement for a short-circuiting, etc., of the triac 2 is performed, and a failure diagnosis for the heater circuit including the triac 2 is performed. At the time of deficiency, a magnet relay 1 and the triac 2 are put under an open mode, and power connection to the auxiliary heater 4 is stopped, and the temperature of the auxiliary heater 4 is prevented from abnormally ascending.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary heater used together with an air conditioner in which energization is controlled by a switching element controlled by a control signal. The present invention relates to an improved temperature control method.

[0002]

2. Description of the Related Art When a failure occurs in a conventional auxiliary heater, protective parts such as a temperature relay, a temperature fuse, and a current fuse, which are inserted in series with the auxiliary heater, are used to adjust the characteristics of each part depending on temperature or current. When an abnormality occurs, the heater circuit is cut off directly, and the power supply to the auxiliary heater is stopped to perform protection. In addition, the temperature thermistor that detects the blowout temperature sends a control signal to the relay when an abnormal temperature pattern is detected, and opens the relay to stop the power supply to the auxiliary heater. ing.

[0003]

However, in such a conventional method, when a failure occurs in the heater circuit,
It detects the open / close of the temperature relay due to an abnormal temperature rise, the operation of the temperature fuse (break), and the operation of the current fuse (break) due to overcurrent. ， Mainly non-conductivity. In addition, the detection of the blowout temperature is complicated due to the influence of external factors due to the air volume around the auxiliary heater, in addition to the operation settings for cooling and heating, etc., so that the detection of disconnection or short circuit of the heater circuit is mainly used.

In recent years, phase control using a switching element such as a triac has been performed as a method of making the temperature and current of the auxiliary heater constant. Semiconductor components such as triacs may cause short-circuit failure events such as element short circuits. When the auxiliary heater temperature and heater current are variably controlled, it is necessary to simply perform heater circuit disconnection and short circuit detection as well as failure diagnosis including the phase circuit control signal section for phase control. There is.

The present invention solves the above-mentioned problems of the prior art. In addition to detection of heater circuit disconnection and short circuit,
It is an object of the present invention to provide a heater circuit control method for performing a failure diagnosis including a phase circuit control signal section.

[0006]

In order to achieve this object, the present invention provides a current flowing through the auxiliary heater by performing phase operation by the switching element for a certain set time after the auxiliary heater is energized. A current transformer that detects the current value compares the current value at that time with a preset current value, diagnoses the failure of the circuit including the switching element, and stops the energization of the auxiliary heater when there is a failure. Is.

[0007]

According to the above method, the auxiliary heater is connected to the relay,
A switching element such as a triac is turned on so that it is energized, and a current flowing through the auxiliary heater is detected by a current transformer. The detected current value and the set current value are compared to carry out a failure diagnosis of the heater circuit, and when trouble occurs, the energization of the auxiliary heater is stopped.

[0008]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of the present invention and is a heater circuit diagram. In FIG. 1, 1 is a magnet relay, 2
Is a triac which is a switching element, 3 is a current transformer for detecting a current, 4 is an auxiliary heater, 5 is a magnet relay control circuit section for controlling the magnet relay 1, 6 is a triac control circuit section for controlling the triac 2, 7
Is a current transformer control circuit unit that controls the current transformer 3,
Reference numeral 8 is an auxiliary heater control circuit unit having a magnet relay control circuit unit 5, a TRIAC control circuit unit 6, and a current transformer control circuit unit 7, which are related to each other.

Next, the operation of the above embodiment will be described. First, the magnet relay 1 is turned on and the triac 2,
The auxiliary heater 4 is energized via the current transformer 3. The phase operation is performed by the triac 2 for a certain set time after the energization of the auxiliary heater 4 is started. A current transformer 3 for detecting a current flowing through the auxiliary heater 4 compares the current value at that time with a preset current value. At this time, if no current is flowing, a failure such as a contact failure of the magnet relay 1, a conduction failure of the triac 2, a disconnection of the auxiliary heater 4, or an abnormality of the phase signal, a disconnection of the heater circuit due to an incorrect connection is determined. If the current is less than the specified value, failure determination such as deterioration of the triac 2, difference in capacity of the auxiliary heater 4 or deterioration, or abnormal output of specified phase signal is performed. Also, when the current is larger than the specified value, failure determination such as deterioration of the triac 2, difference in capacity of the auxiliary heater 4 or deterioration, or abnormal output of specified phase signal is performed.

When the current value detected by the current transformer 3 is large and the current value remains unchanged even if the phase control is performed, it is judged whether the triac 2 is short-circuited or not, and the circuit failure including the triac 2 is diagnosed. In case of trouble, by setting the magnet relay 1 and triac 2 to open mode,
It is possible to stop the energization to the auxiliary heater 4 and prevent a dangerous matter caused by an abnormal rise in the temperature of the auxiliary heater 4.

[0011]

As described above, according to the present invention,
As a method of making the temperature and current of the heater constant, in a heater circuit that performs phase control using a switching element such as a triac, in addition to disconnection of the heater circuit, element short circuit of semiconductor parts such as triac, deterioration of the switching element, Further, it is possible to discriminate a failure event including the phase circuit control signal portion for performing the phase control and perform more detailed failure diagnosis. Further, by using the current flowing through the heater, it is less likely to be affected by the operation settings such as cooling and heating of the air conditioner and the change in the air volume due to the fan speed, so that the detection accuracy can be improved. This has the effect of enabling control with improved safety without adding more parts.

[Brief description of drawings]

FIG. 1 is a heater circuit diagram in an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnet relay, 2 ... Triac, 3 ... Current transformer, 4 ... Auxiliary heater, 5 ... Magnet relay control circuit part, 6 ... Triac control circuit part, 7 ... Current transformer control circuit part, 8 ... Auxiliary heater control circuit part.

Claims (1)

[Claims] 1. An auxiliary heater used together with an air conditioner,
In a method of controlling energization by a switching element controlled by a control signal, after starting energization of the auxiliary heater, a phase operation is performed by the switching element for a certain set time, and a current for detecting a current flowing through the auxiliary heater. An air conditioner characterized by comparing a current value at that time with a preset current value by a transformer, diagnosing a circuit failure including the switching element, and stopping the energization to the auxiliary heater when a failure occurs. For controlling heater circuit of machine.